Electric ladle furnace



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ELECTRIC 1.1mm FURNACE Filed llay 14, 1949 3 Sheets-Sheet 2 INVENTOR.

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Y mwxmaw Oct. 17, 1950 Filed lay 14, 1949 a crucible for molten metal.

Patented Oct. 17, 1950 ELECTRIC LADLE FURNACE Vernon H. Ferguson, Mount Lebanon, Pa., as-

signorto Loftus Engineering Corporation, a

corporation of Maryland Application May 14, 1949, Serial No. 93,243

1 My invention related to furnaces, particularly to ladle furnaces for use in handling molten metal in foundries and other industrial shops.

A ladle furnace of the sort in mind consists in The crucible isinstalled within a refractory-lined body or shell, with a space providedbetween the walls of the crucible and the shell for electrical heating elements (or for hot products of combustion) to heat and maintain the molten metal within the crucible at desired temperature. The entire structure is adapted to be pivotally supported by means of a bail that can be engaged by an overhead crane, or the like, and on such pivotal support the ladle structure is arranged to be tilted, whereby molten metal may be poured or teemed from the crucible as required. My invention consists in certain new and use- 'ful structural improvements in ladles or ladle furnaces of this type, to the end that thermal efficiency is obtained in largest measure, together with increased economy and durability of structure.

From time to time the crucibles of such ladles fail in service, with the result that molten metal 5 Claims. (CI. 1321) escapes into the space within the refractory-lined body or shell. This requires that the ladle structure be taken out of service and the molten metal, then solidified, removed. This is the difficult task, and in the case of electrically heated ladles, there is danger of destroying or damaging the heating 7 elements.

In further accordance with the objects of my invention, I provide a false bottom on the refractory-lined body or shell. This false bottom is arranged at an interval below the normal refractory-lined bottom of the shell, providing an aux iliary chamber. Passages are formed in the normal bottom of the refractory-lined body and these open into the auxiliary chamber, whereby molten metal (escaping due to the failure of the crucible) runs into the auxiliary chamber where it is accumulated and solidified. The false bottom is readily dismountable, for the removal of the solidified metal.

In the accompanying drawings a ladle furnace comprising an exemplary embodiment of the invention is illustrated in the drawings:

Fig. 1 is a view of the ladle furnace in front elevation;

Fig. 2 is a sectional view of the ladle furnace, as seen on the plane II'II of Fig. 1;

Fig. 3 is a diagrammatic View of a mechanism included in the structure for manually tilting the ladle on its pivotal support;

Fig. 4 is a view in medial horizontal section through the ladle, illustrating a modification in structure; I

Fig. 5 is a view partly in side elevation and partly in vertical section of a ladle embodying still other modifications in structure; and

Fig. 6 is a fragmentary view in vertical section, showing the lower portion of the modified ladle structure of Fig. 5 to still larger scale.

Referring to the drawings, the ladle structure comprises an outer shell 2, cylindrical in this case, formed of steel plate. Above the center of gravity of the ladle structure, trunnions 3 are secured upon opposite sides of the shell in axial alignment, and to these trunnions a bail 4 is attached, the bail having an eye 5 whereby the entire structure may be engaged, lifted and transported by means of an overhead crane.

On one side of the ladle a hand-wheel 6 is geared to the adjacent trunnion 3, by means of which the ladle structure, when suspended from a crane, may be manually tilted, to pour or teem molten metal from a spout l, as will presently appear. The gearing between the hand-wheel 6 and the adjacent trunnion 3 consists in a wormgear 8, a worm 9, and two bevel gears l0 and II.

The bevel gear H is integral with the axis of the may be tilted as required. The engagement of the teeth of the worm .l with the teeth of the Worm-gear 8 serves as a mechanical lock to prevent the tilting of the ladle from any position into which the ladle is adjusted. 1

A refractory lining I3 is provided within the body or shell 2, the refractory lining or partition at the bottom of the body being borne on a plate I4 secured to an annulus l5 of angle shape in cross-section, welded to the steel plate which in this case the stool being formed of a chrome-12% nickel Steel alloy. It will be noted that the stool consists in an open ring portion 19, upon which the crucible immediately seats, and from said ring portion a plurality of spaced legs 28 extend downward through the refractory floor of the chamber 6 to the metal plate M that forms the normal bottom wall of the chamber.

Over the top of the structure a refractory-lined metal cover 2! is removably secured by means of screws 22.

The means for melting, heating and maintaining a charge of metal within the crucible I! in the desired molten condition consists in electric resistor elements 23 supported on insulators 24, which protrude inwardly from the refractory wall or lining is into the space provided between such lining and the wall of the crucible. Electrical cable 25 carries from a suitable source electric current to the resistor elements 23, and in known way such elements are energized to generate the required heat. It will be noted that the stool is of open construction, providing a passage beneath the crucible, whereby the heat generated within the chamber l6 will be distributed and applied uniformly over all of the surface areas of the crucible.

The refractory-lined body 2 is provided with a false bottom 26 which is spaced at an interval below the normal refractory bottom of the chamber 16. The bottom 26 consists of a heavy plate of steel welded to an annulus of angle shape in cross-section, and is secured to the outer shell 2 by means of r movable screws 28 passing through the vertical flange of said annulus into threaded engagement with shell 2. This structure. provides an auxiliary chamber 29 below the chamber 56 in which the crucible is positioned. From the chamber l6 downwardly divergent passageways 3-3 open into the auxiliary chamber 29. If and when the crucible i! cracks or wears through in service, the escaping molten metal quickly flows through the passages 38 into the auxiliary chamber 29. In this way the molten metal does not accumulate in the chamber l6 where it may contact and short-circuit the resistors 23. Furthermore, if and when the crucible fails in service, the resistors 23 are deenergized to allow the structure to cool to the extent necessary to insert a new crucible. But for the improvements of my invention the escaping molten metal would accumulate and solidify in the bottom of the chamber IE, thereby presenting a difiicult problem. However, in

the structure described, the molten metal (regardless of the degree of tilt of the ladle structure when failure of the crucible may occur) runs into the chamber 25), where it solidifies.

The false bottom 26 of the auxiliary chamber 29 comprises a removable wall section, it being merely necessary to remove the screws 23 and remove the false bottom and dislodge the accumulated metal. The ladle may be quickly reconditioned for continued service.

In the case of certain metals, there may be a tendency for the metal to stick or adhere upon solidification to the walls of the auxiliary chamber 29. In prevention of this, the auxiliary chamber is lined with a refractory and readily separable or frangible material, such as sheet asbestos 3!. When a mass of accumulated metal has been removed from the auxiliary chamber, the lining 3! may be readily renewed.

Such is the construction of a ladle furnace of my invention. The top 2| is readily removable for giving access to the internal parts of the structure for cleaning or repair. It is unnecessary to dwell upon the manner in which the ladle furnace is operated. Those skilled in the art will readily understand. Sufiice it to say, that a batch metal may be melted and alloyed by the introduction of a suitable charge into the crucible, and, when in molten condition, the metal may be maintained at specified temperature for the intended use.

While the ladle structure described above is arranged for electrical heating of the crucible, in modification the structure may be designed for heating by means of a fluid fuel. As shown in Fig. 4, the chamber l6 between the refractory lining l3 of the outer body and the wall of the crucible I! may comprise a combustion chamber, and through the shell 2 and refractory lining l3 one or more burners 32 may be directed, tangentially as shown in Fig. 4. A mixture of gaseons or liquid fuel and combustion air may be delivered by the burners 32, and combustion maintained in the chamber I6 at the desired rate, to heat and maintain the metal in the crucible at proper temperature. The products of combustion may be vented through one or more ports 33 formed in the wall of the refractory-lined body of the ladle structure.

Whereas the ladle structure first described in the foregoing specification is provided with electrical resistor elements mounted in the space between the refractory wall of the ladle chamber and the wall of the crucible, in the modified structure of Figs. 5 and 6 the resistor elements 23a are embedded in refractory units 24a, and the leads from the resistor elements 23a are extended downward through the refractory bottom of the structure, ending in terminals 34 which are accessible in an annular raceway 35 (Fig. 6). Such organization of electric resistor elements within a refractory-supporting structure is old, and forms no part of my invention, except in the features of organization of such elements with the ladle structure in which they are described.

In the modified structure of Figs. 5 and 6, it will be noted that the crucible Ila is supported upon the refractory bottom of the ladle body; that is, the legs 20a which carry the cruciblesupporting ring [9a of heat-resisting alloy are fixed at their lower ends to a ring 20?) which rests upon the refractory bottom.

The false bottom 26a (Fig. 6) is removably secured by screws 28a to an annulus 21a of angle shape in cross section. An anglo-shaped annulus 36 is welded to the lower. edge of the shell 2a, and a plurality of vertical legs 31, also of angle shape in cross section, are welded to the annuli 21a and 36, whereby a rigid support is furnished for the false bottom 260..

A conical wall 38 is welded at its upper edge to the bottom plate 14a of the structure, and at its lower edge is welded to the inner periphery of the annulus 21a. The auxiliary chamber 29a, which is adapted to receive the escaping molten metal in case of crucible failure, is formed by the bottom plate Ma, the conical or vertically extending wall 38 and the false bottom 26a. Between the annuli 21a and 36, a cover plate 39 extends circumferentially of the ladle structure. The cover plate 39 may be formed in sections, secured by means of screws 40 to the angle members 31. It will be perceived that an annular raceway is thus formed, a raceway 35 which i entirely enclosed, to form a housing chamber for the disposal of metal accumulated for the electrical conductors (not shown) which connect the terminals 34 of the resistors 23a to the contact members of a conventional plug-in receptacle 4|, by means of which the electrical feeder lines for energizing the resistors may be readily connected or disconnected. The enclosed raceway 35 may be opened for inspection or repair of the electrical conductors and housed therein, by merely removing the cover plate 39.

The auxiliary chamber 29a provides, as in the structure first described, a safe accumulation space for molten metal that escapes in the case of failure of the crucible. It is a simple matter to remove the false bottom 26a and clean away the molten metal when it has solidified.

Notice is given of my divisional application for Letters Patent, Serial No. 139,896, filed January 21, 1950.

Within the terms of the appended claims various modifications and changes in the ladle structure may be made by the mechanic without departing from the spirit of the invention.

I claim:

1. A ladle furnace for molten metal comprising a refractorylined metal shell forming a crucible chamber, a crucible for molten metal, means borne by the wall of said chamber for supporting said crucible at an interval above the refractory lining at the bottom of said chamber, means arranged within the walls of said chamber for developing heat to maintain the contents of said crucible in molten condition, the side wall of said shell extending downwardly from said chamber to provide an auxiliary chamber for receiving and retaining molten metal in case of a failure of said crucible, a port opening through the floor of said crucible chamber into said auxiliary chamber, said auxiliary chamber being provided with a false bottom, and means for detachably securing said false bottom to said downwardly extended side wall of said shell, whereby said false bottom may be removed to open said auxiliary chamber for the disposal of metal accumulated therein, and a thin lining detachably applied to the internal surfaces of said auxiliary chamber.

2. A tilting ladle furnace for molten metal comprising a refractory-lined metal shell formmg a crucible chamber, pivotal means supporting said furnace for tilting movement, a crucible for molten metal, means for securely mounting the crucible in said chamber and above the bottom of the chamber for tilting movement in unison with the furnace, electrical resistors arranged within the walls of said chamber for developing heat to maintain the contents of said crucible in molten condition, the side wall of said shell extending downwardly from said chamber to provide an auxiliary chamber for receiving and retaining molten metal in case of a failure of said crucible, said auxiliary chamber being provided with a false bottom, means for detachably securing said false bottom to said downwardly eX- tended side wall of said shell, wh eby saldfelse bottom may be removed to Op Said auxlhary therein, the refractory lining of said crucible chamber bottom being arranged at an interval below said resistors and said refractory iined bottom including at least one port opening downwardly into said auxiliary chamber, whereby in case of a failure of said crucible the molten metal may escape into said auxiliary chamber without damage to or short-circuitingof said resistors.

3. A tilting ladle furnace for molten metal comprising a refractory-lined metal siiell forming a crucible chamber, pivotal means supporting said furnace for tilting movement, a cruc ble for molten metal, means for securely mounting the crucible in said chamber and above the bottom of the chamber for tilting movement in unison with the furnace, means spaced above the floor of said chamber for developing heat within the walls of said chamber to maintain the contents of sa d crucible in molten condition, the side wall of said shell extending downwardly from said chamber to provide an auxiliary chamber for rece ving and retaining molten metal in case of a failure of said crucible, a port opening through the bottom of said crucible chamber into said auxil ary chamber, said auxiliary chamber being provided with a false bottom, and means for detachably securing said false bottom to said downwardly extended side wall of said shell, whereby said false bottom may be removed to open said auxiliary chamber for the disposal of metal accumulater therein.

4. The structure of the next-preceding claim, said crucible-mounting means comprising a stool formed of heat-resisting and heat-conducting material and such stool having a plurality of legs extending upwardly from the bottom of said refractory-lined crucible chamber and providing between the stool legs open passages below the supported crucible for enhancing a distributed application of heat to the walls of the crucible.

5. The structure of the next-preceding claim, in which a thin lining is detachably applied to the internal surfaces of said auxiliary chamber.

VERNON H. FERGUSON.

REFERENCES CITED The following references are of record in the file of this patent:

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